Piezo-electric-crystal apparatus



IDern 27, i1927.

E. I PowELL PIEZO ELECTRIC CRYSTAL APPARATUS Filed Dec. 29, 1925 f INVENToR. fafa/yal awe ATTORNEY Patented Dec. 27, 1,927.

UNITED STATES-J j .1,654,1e9 PATIENT OFFICE.

EDWIN I.. POWELL, or wAsHINo'roN, DISTRICT orcownnu, .as'sIoNon 'ro wnuzn name, INC., or-Nnw Yonx, N. Y., a CORPORATION or Dmwm;

rIEzo-ELncrmqcnstmr. Arr'anurus.

`Application lled December 29, 1925. Serial ANo. 78,208.

My invention relates broadly to signal -receiving systems and more particularly to a piezo electric crystal apparatus for use in such systems, y j

One of the objects of my invention 1s to provide a construction of piezo electric crystal apparatus which ma be readily connected in present constructions of signal receiving apparatus for indicating the frequency at which the apparatus is responsive.

Another object of lny inventionis to provide a piezo electric crystal apparatus which may be interposed in a signal receiving circuit to permit an exact'setting or re-setting of the receiving circuit to a plurality of ranged with relation to the cylindrical support for making connection between any selected crystal and a signal receiving circuit for indicating the frequency of the circuit with respect to incoming signaling energy of a pre-determined frequency.

A further object of my invention is to I provide a construction of a multiple crystal.

holder' for signal receiving circuits, in which. a plurality of independent piezo electric crystals are longitudinally positioned along the sides of a metallic drum which forms one side of a capacity area, with which the surfaces of the piezo electric crystals cooperate, connection being made capacitively with the opposite side of a pre-determined piezo electric crystal by rotatively moving the selected crystal in desired capacity relationship with a stationary plate.

Other and further objects of `my invention will be understood from the specifica- -tion hereinafter following, by reference to the accompanying drawings, in which:

Figure 1 is a full sized cross-sectional view taken through the multiple electric crystal holder; Fig. 2 is an end view of the multiple crystal holder taken on line 2 2 of Fig. 1; Fig. 3 isa view showing the indicating means from the front of the receiver panel, with control knob removed, taken along line 3--3 of Fig. 1; Fig. 4 is an enlarged cross-section taken on line 4 4 of Fig'. 1, showing `the capacitive relation lof the high potential electrode 51 to the crystal enclosing grooves of the drum 1'; and Fig. 5 shows the electrical connections of the multiple crystal holder with an electron tube signal receiving circuit.'l

I-have illustrated my invention as being particularly adaptable for application in a signal receiving'circuit of a radio receiving system which can be employed either with an antenna ground system for space radio operation or employed in connection with a line wire system for wired radio operation. My invention embodies the capacity coupling of a quartz crystal, or other constant frequency generator to the grid filament circuit of an electron tube oscillating detector for the production of a musical click kin telephones, which may be connected inV theoutput circuit of the Idetector,-which .musical .click occurs when the frequencyof 'the oscillating circuit is tuned "across the resonant period of the crystal. The establishment of. a musical click for predetermined frequencies permits a positive setting orresetting of the circuit to a desired frequency. f "In the piezo electric crystal apparatus 'of-myinvention, I make provisionrfor nineteen. different settings of the receiver equipment by 'virtueof quartz or piezo electric crystalswhich are accurately ground to the selected frequencies.` I provide a metallicdrum having means for receiving a=plurality ofseparate piezo electric crystals each having different frequency characteristics and each, when the drum is set in the off position, being completely shielded electrostatically by the drum and its surrounding metal case, these being connected electrically to the low potential or ground side of the oscillating c1rcuit. The several crystals are retainedv in grooves cutlongitudinall on the periphery ofthe drum by an encirc ing sheet of transparent celluloid or other dielectric material and plugs of hard rubber wedged into the ends of the grooves. The crystals'rest loosely in their respective compartments, however, that they may be free to vibrate mechanically when subjected to electrostatic strains produced by high frequency electrical oscillations of the same frequency as their resonant periods. Although I have shown an insulating con-l tour on the surface of the drum which serves as a cushion between the crystals and the drum it should be understood that this may be eliminated in practice and the crystals allowed to rest in direct contact with the drum. I further rovide a longitudinal slot in the surrounding case slightly wider than one of the crystal grooves, and support a plate electrode therein which is connected to the high potential side of the oscillating electron tube detector circuit, so that any one of the crystals may be rotated thereunder and thus subjected to the electrostatic strain which exists between said plate electrode and the grounded case., all other crystals remaining shielded from said strain.

Referring to the drawings in more detail, reference character 1 represents a metallic drum secured to a metallic shaft 2 by a taper pin 3. This drum has nineteen longitudinal grooves represented by reference character 70, and one narrow slot 71, equally spaced about its periphery, with twenty corresponding depressions 72 on the rear face of the drum operating in Aconjunction with a (flicker ball 4 and a spring 5 serving to hold the drum in any of twenty angular positions. 6 represents a thin piece of fish paper or other material forming a resilient surface contour to the drum 11. 7-25 represent quartz crystals, of which there are nineteen, having equal cross-sectional area's of such dimensions as to lay loosely in the insulated grooves of drum 1, their longitudinal or Y axes being determined by the frequency desired. 26-44 represent nineteen pairs of hard rubber plugs forming tight fitting closures for the extremities of the crystal grooves, the respective lengths of each pair being selected to allow about 15 free end motion to the corresponding crystal. These plugs serve the double function of centering the respective crystals under the high potential electrode and preventing the ends of the crystals from scraping on the ends of the container. They also serve as wedges for holding the cushioning strip G in close conformity with the grooved surface of the drum.

45 is a second strip of transparent celluloid or other insulating material which is drawn tightly around the exterior of the drum and secured by a piece of red fiber 46, which wedges the ends into the narrow slot in the surface of the drum. This wedge, by reason of its distinctive color, also serves as an index marker, which can be viewed through a peep hole 73 in the rear end plate 47 of the container, for use in locating the off position when assembling the dial at the time the instrument is to be installed in a receiver. The spindle 2 rotates in bearing apertures in the aluminum end plates 47 and 48, the forward end plate having a bracket 49 attached thereto for securing the completed unit to the' rear of a receiver subpanel. These end plates are spaced apart by a thin walled brass cylinder 50, complete ly enclosin the drum assembly except for a bevelled et gc slot 74, cut longitudinally in its upper surface, the dimensions of the opening being somewhat larger than those of the largest crystal.

A high potential metallic electrode 51, having surface dimensions equivalent to those of the largest crystal is centrally supported within this opening by means of a hard rubber bridge 52, which is secured to the end plates 47 and 48. Spacing washers 53 are provided between the hard rubber support 52 and the electrode 51 for the purpose of reducing capacity and. dielectric losses, and a terminal lug 54 serves for connecting the electrode to the high potential side of the received secondary circuit. A second terminal lug 55, mounted on the forward end plate 48, provides connection means between the metallic frame of the unit and the illament or low potential side of the receiver secondary circuit.

The forward end of the shaft 2 is flattened on two sidesto prevent relative rotation bctween it and the dial hub 56 which is assembled behind the main receiver panel 75. This hub carries a white Celluloid dial 57, around the outer edge of the forward face of which are engraved the word Off and nineteen framed spaces in which can be lettered 'the respective frequencies corresponding to the nineteen crystals selected, a peep hole 7 6 drilled at proper alignment therewith through the main panel serving as the selective indicator therefor. Cont-inuing through a hole 77 in the main panel, the flattened end of spindle 2 passes through a broached knob seat 58 which has two holes drilled in its face to receive the projecting pins molded in a central knob 59. A machine screw G0 passing through the center of the knob secures the entire indicating and control means to the end of the shaft 2.

In Figure 5 I have illustrated the connection of the frequency indicator of my invention in an electron tube circuit where reference characters 8() and 81 designate a tuning system which is connected with the input circuit of an electron tube detector 82 having grid leak and grid condenser 83 in the grid circuit thereof. The output circuit of the electron tube detector 82 is illustrated as including coupling coil 84 and responsive device 85, and high potential battery 86. The frequency indicator is connected directly across the input circuit of the electron tube 82 and in shunt with the tuning condenser 81. As illustrated, the shaft 2 may be revolved to present any selected piezo electric crystal of the series 7-25 to a position below the stationary electrode 51 for subjecting it to the electrostatic strain developed by the oscillating circuit. The shield 50 serves to prevent said electroloo llU

static strain from acting upon the remaining piezo electric crystals of frequency characteristics differing from that of the one selected.

The frequency indicator is arranged for installation in a complete radio receiver and in the Off position represented in Fig. 4, that is, in the position Where the fiber wedge 46 is presented immediately below the stationary electrode 51, an the character designation Off on indicator card 57 appears through the sight opening 76 in the panel 75, there will be no effect on the operation of the circuit other than a possible minute change in the original calibration caused b the added capacity of the high potential electrode (not more than five micro microfarads), since in this Off position each of the piezo electric crystals is completely surrounded by the grounded metallic case 50 and the drum l, and when thus shielded cannot react to oscillation in the receiving circuit. However, by turning the control knob and rotating shaft 2 to any one of the selected positions ofthe rotatable carrier by virtue of the detent mechanism 4-5-72, a selected piezo electric crystal may be presented through the gap 74 in the shield 50 below the stationary electrode 51. The fixed frequency characteristic of the particular piezo electric crystal in a particular groove has a corresponding designating character noted on the indicator card 57 which appears through the peep-hole 76 in panel 7 5. By this arrangement the operator may place a desired piezo electric crystal in capacitive relation to the high potential or grid electrode 51 whereas the eighteen undesired crystals remain completely and individually shielded.

In the views illustrated it is not possible to gain any conception of the relative sizes of the piezo electric crystals 7-25. In the p 'actical construction of my invention the pockets around the surface of the rotatable carrier vary in size, by reason of the fact, that the piezo electric crystals vary from an extremely short crystal to a relatively long crystal in stepped formation around the surface of the rotatable carrier. In a number of instances, I have found it practical to eliminate the cushioning material in the several pockets allowing the crystals to make direct electrical contact with the metallic carrier 1.-

In the operation of the frequency indicator of my invention I am enabled to secure adjustment of the electron tube receiving circuits for a desired signaling frequency by rotation of the control shaft 2 to a position where a transient musical click may be observed in the telephone when the frequency of the oscillating circuit is tuned across the .resonant period of the crystal. In this manner the receiver may be accurately adjusted to a plurality of different frequencies without the necessity of resorting to the useof a separate wavemeter or other cumbersome means.

While I have described a preferred embodiment of my invention I desire that it be understood that modifications lnay be made and that no limitations upon the invention are intended other than those imposed by the scope of the appended claims.

What I claim and desire to secure by Letters Patent of the United States is as follows:

1. Piezo electric crystal apparatus comprising in combination a cylindrical rotor having a plurality of longitudinally extending grooves along the surface thereof` pockets formed by end closures in said grooves, piezo electric crystals of differing frequency eharacterist-ics carried in said pockets` and means positioned adjacent to said cylindrical rotor and extending parallel with the axis thereof for selecting a particular piezo electric crystal from said plurality of piezo electric crystals, and utilizing the piezo electric effect of said crystal to the exclusion of that of others of said crystals.

2. Piezo electric crystal apparatus comprising in combination a rotatable shaft member, an indicator card carried by said rotatable shaft member, a Yylindrical rotor mounted on said rotatable shaft member, said cylindrical rotor having a plurality of longitudinally extending grooves on the surface thereof corresponding to designated posit-ions on said indicator, cushioned pockets carried in said grooves. a pluralityof piezo electric crystals of differing frequency characteristics located in said pockets, and

mea-ns located adjacent said cylindrical rotor for effectively utilizing the piezo electric effeet of a selected one of said crystals to the exclusion that of others of said crystals when said indicator card is moved to a position where the selected designation corresponding to the selected piezo electric crystal may be observed.

3. Piezo electric crystal apparatus comprising in combination a rotatable carrier, a plurality of piezo electric crystals of differing frequency characteristics supported in said rotatable carrier, and means supported adjacent said rotatable carrier for effectively utilizing the piezo electric effect. of a selected one of said piezo electric crystals to the exclusion of that of others of said piezo electric crystals when said rotatable carrier is moved to a selected position.

4. Piezo electric crystal apparatus comprising in combination a rotatable carrier, a plurahy of piezo electric crystals each having di ering frequency characteristics supported by said rotatable carrier, a stationary electrode mounted adjacent said rotatable carrier, and means whereby said rotatable lui) carrier may be moved to selected positions for presenting a selected piezo electric crystal beneath said electrode for effectively utilizing the iezo electric effect of the selected piezo e ectric crystal to the exclusion of that of o thers of said piezo electrical crystals.

5. Piezo electric crystal apparatus comprising in combination a cylindrical rotatable carrier, a plurality of piezo electric crystals supported adjacent the surface ot said rotatable carrier longitudinally of the axis thereof, and a stationary electrode -longitm'linally aligned with the axis ot said rotatable carrier for effectively utilizing the piezo electric effect of a particular piezo electric crystal when said rotatable carrier is moved to a selected position below said. electrode, and means 'for preventing interference l'rom the piezo electric effects of others ot said piezo electric crystals.

6. Piezo electric crystal apparatus coinprising in combination a rotatable support ot conducting material, a plurality of piezo electric crystals ot differing` frequency characteristics mounted in said support, means for centering each ot said crystals with respect to said support. a stationary electrode mounted adjacent said support and arranged to overlie a selected one of said crystals when said support is moved to selected positions with respect to said electr0de,"and conducting means surrounding and functioning with said rotatable support for preventing false 'resonance indications beingr produced by said piezo electric crystals other than that developed by th'e selected `one of said piezo electric crystals when the selected piezo electric crystal is presented belon7 said stationary electrode.

7. Piezo electric crystal apparatus coinprising in combination a metallic drum, means for rotating,r said drum into an individual one of a plurality of different anafular positions, a longitudinally extending' groove formed in the surface of said drum for cach angular position thcreot, cach ot saidvgroovcs forming a pocket .for receiving piezo electric crystals ot differing frequency characteristics therein, a stationary metallic shell substantially surrounding said drum and having a gap therein substantially the size ot one of said pockets, a stationary electrode projecting through said lrap and having a metallic face thereon to Which each of said piezo electric crystals may be pre sented for effectively utilizing the piezo electric eii'ect of a selected piezo electric crystal to the exclusion of that of others ot said piezo electric crystals.

EDWIN L. POVELL. 

